Testosterone study finds differing disease links in men and women

The findings, from the largest study to date on links between testosterone and disease, show the importance of studying men and women separately, the scientists who led the research said - and point to the need for caution in using testosterone supplements or hormone-reducing therapies.

The team, whose work was published in the journal Nature Medicine, used genetic data from more than 425,000 people registered in the UK Biobank to identify 2,571 genetic variations linked to differences in levels of testosterone.

Using statistical analyses and cross-checking their results, they found that in women, having genetically higher testosterone increases the risk of developing type 2 diabetes by 37%.

High testosterone also raises the risk of breast and endometrial cancers in women, the study found, and increases the risk developing polycystic ovary syndrome - a hormonal disorder that affects menstruation - by 51%.

In men, however, the researchers found that having higher testosterone levels reduces type 2 diabetes risk by 14% but also raises the risk of developing prostate cancer.

The results give a unique insight into the disease impacts of testosterone, and “emphasise the importance of considering men and women separately in studies, as we saw opposite effects for testosterone on diabetes,” said Katherine Ruth, a genetics specialist at Britain’s Exeter University who co-led the study.

John Perry, an expert at Cambridge University who worked with Ruth, said the findings add to scientists’ understanding of the potential risks and benefits of hormone therapies.

“In men, testosterone-reducing therapies are widely used to treat prostate cancer, but until now it was uncertain whether lower testosterone levels are also protective against developing prostate cancer,” he said.